In recent years, attention has been paid to influences of active oxygen and free radical upon organisms. Active oxygen and free radical are always generated and eliminated within an organism as long as the organism continues to live while using oxygen. In general, they act advantageously to the organism as a part of organism protection. However, when they are generated in an amount exceeding the protecting ability of the organism against the radical, they may attack the components of the organism constituting membranes and tissues of thereof, thereby causing various pathologies and malignancies. At present, the pathologies and diseases which may be attributable to active oxygen and free radical are numerous and their examples include cerebral nerves diseases such as brain infarction, brain edema, and parkinsonism; lung diseases such as lung oxygen intoxication and adult respiratory distress syndrome; circulation system diseases such as ischemic heart diseases (e.g., myocardial infarction and arrhythmia), and arteriosclerosis; and digestive organs diseases such as peptic ulcer, ulcerative colitis, and Crohn's disease.
Under these circumstances, consequently, there have been attempts to apply scavengers of active oxygen and free radical to medicaments for the above-mentioned diseases. For example, with respect to brain edema, mannitol, which is a mild radical scavenger, has been clinically used, though it is necessary continuous administration for two weeks. Recently, radical scavengers such as AVS (currently being applied) and MCI186 (currently being clinically tested in the third phase) have been developed recently. The sole target disease of these compounds is, however, brain edema. There has been no medical drug in which a radical scavenger is used for suppressing brain infarction.
On the other hand, a recombinant of SOD has become available and has been administered to patients so as to study its tissue-protecting effect. Acute myocardial infarction is one of its target diseases. By contrast, no radical scavenger other than SOD has been known as a medicament for this disease. With respect to arrhythmia, on the other hand, only lidocaine, which is a local anesthetic, has been clinically used.